Re: A bug in Show[]?

*To*: mathgroup at smc.vnet.net*Subject*: [mg88570] Re: [mg88559] A bug in Show[]?*From*: Carl Woll <carlw at wolfram.com>*Date*: Fri, 9 May 2008 03:21:19 -0400 (EDT)*References*: <200805080815.EAA14372@smc.vnet.net>

Alexey Popkov wrote: >Hello, >Consider the following combined plot: > >model[i_] := Log[i] - Log[i - 1]; >Show[Plot[(model[ii]), {ii, 2, 51}], > ListPlot[Table[{im, model[im]}, {im, 2, 51}]], PlotRange -> All] > >You may see that a part of first Plot is absent. It is easily to >demonstrate that only a part of Plot that is not shown without the >option "PlotRange -> All" is absent: > >Show[Plot[(model[ii]), {ii, 2, 51}], > ListPlot[Table[{im, model[im]}, {im, 2, 51}]]] > >The workaround is to put this option inside first Plot[] instead >outside of those: > >Show[Plot[(model[ii]), {ii, 2, 51}, PlotRange -> All], > ListPlot[Table[{im, model[im]}, {im, 2, 51}]]] > >But in documentation for Show[] one can read: "Options explicitly >specified in Show override those included in the graphics >expression.". Thus this is a bug in Show[]! > >Moreover placing this option inside the second command ListPlot[] has >no result at all (the option is ignored): > >Show[Plot[(model[ii]), {ii, 2, 51}], > ListPlot[Table[{im, model[im]}, {im, 2, 51}], PlotRange -> All]] > >But according to the documentation "The lists of non-default options >in the Subscript[g, i] are concatenated.". Thus it seems to be the >second bug in Show[]! > > The documentation says: Show can be used with Graphics and Graphics3D. So, Show can override the options in Graphics and Graphics3D objects. Now Plot isn't a Graphics object until it is evaluated, and the options to Plot will determine what kind of Graphics object is created. In this case, the Graphics object created when using PlotRange->Automatic is different from the Graphics object created when using PlotRange->All. Basically, more points are included in the Line primitive in the Graphics object when Plot is used with the PlotRange->All option. Changing the PlotRange option of a graphic created using the PlotRange->Automatic option will not cause these additional points to magically appear. Carl Woll Wolfram Research

**References**:**A bug in Show[]?***From:*Alexey Popkov <popkov@gmail.com>